The objectives of this proposal are to: a) Simulate new perturbation experiments, expand the saccharide interconversion model to include ATP and Pi turnover, model the mechanism of trehalose-6-P synthase and seek further experimental evidence that G6P is compartmentalized. b) Carry out additional experimental and simulation analyses in order to finalize the TCA cycle steady state model, and do flux studies for the construction of a steady state model of pentose metabolism at 3 stages of development. c) Model the TCA cycle and pentose metabolism over the course of differentiation and aging, and construct a saccharide interconversion model for each cell type.